Python 3 2, 79 74 69 65 bytes

def s(x):
 i=l=len(`x`)
 while(i<=x):print"\b"+`i`.zfill(l);i+=l

My new model is based on Karl's model based on my model, I'm not sure if that is fair or not

increments the number to be printed by length of input, prints it with proper amount of zeros, until number is equal or greater (shouldn't be greater though)

\b is backspace